Recently, in the field of the construction machine such as a hydraulic excavator, as a remedy for situations that aggravate the working environment such as exhaust gas and noises, a variety of hybrid drive units have been proposed, in particular, an energy regenerative device for a construction machine that enables efficient energy recovery which is the advantage of a hybrid system.
The Applicant proposed in the Patent Document 1 the art relative to a construction machine with a hybrid drive unit, wherein the inertia energy of a comparatively large inertia object such as a boom of a hydraulic excavator and a upper revolving structure is effectively regenerated, and wherein there is no need for supplementary recharging to an electric storage device for an electric motor/power generator.
FIG. 3 is an overview diagram of the conventional hydraulic excavator. As illustrated, the hydraulic excavator comprises: a lower traveling body 102 having a right/left endless track caterpillar band 102A as a travelling means; a upper revolving structure 104 revolvably mounted on the lower traveling body 102; a multijoint hydraulic operating machine (front device) 111 that is elevatably connected to the upper revolving structure 104 and that consists of a boom 106, an arm 108 and a bucket 110; a hydraulic cylinder 114 for a boom that drives the boom 106; a hydraulic cylinder 116 for an arm that drives the arm 108; a hydraulic cylinder 118 for a bucket that drives the bucket 110; a revolution hydraulic motor 120 and a velocity reducer 122 that drive the upper revolving structure 104; and hydraulic motors 124L, 124R for right/left travelling that drive the right/left endless track caterpillar band 102A.
A method to employ a regenerative device to this kind of construction machine is described in the Patent Document 1: “When the operator returns the lever of the control valve in order to stop the upper structure, the control unit detects the change of the signal generated from the hydraulic/electric transducer, and a control signal generated in accordance with the data processing program of the control unit is transmitted to the servo driver. In response to this, the servo driver controls the electrical quantity to be supplied to the electric motor, actuates the regenerative mode, and transmits a control signal to the electrical/hydraulic transducing valve. This control signal causes the electrical/hydraulic transducing valve to generate the pressure oil signal, and thereby allows actuation of the communication valve to communicate the two inlet ports of the hydraulic motor such that the braking torque generated in the hydraulic motor becomes minimal, and that most of the inertia energy of the upper revolving structure is intensively supplied to the electric motor functioning as a power generator.” To be more specific, in the Patent Document 1, when the operator returns the lever of the control valve to the neutral position, the control unit detects the change of the signal generated from the hydraulic/electric transducer, causing the regenerative operation.
The Patent Document 2 recites in the paragraph 0059: “The reference numeral ET2 shows that in the acceleration drive mode, an electric energy is supplied from the electric storage device to the power generator/electric motor. The reference numeral ET2 shows that in the deceleration drive mode, an electric energy is supplied from the power generator/electric motor to the electric storage device. The reference numerals xa, xd show the transition of the torque Tm in the acceleration drive and deceleration drive modes of the hydraulic motor. The reference numerals ya, yb show the transition of the torques Te(motor) and Te(generator) in the acceleration drive and deceleration drive modes of the power generator/electric motor.” In sum, “in the deceleration drive mode, an electric energy is supplied from the power generator/electric motor to the electric storage device”, which means the regenerative operation.
Further, the Patent Document 3 describes an energy regenerative device for a hydraulic construction machine mounting an electric motor/power generator, wherein the value of the manipulated variable of the control lever is used to determine whether to actuate the electric motor/power generator as an electric motor or as a power generator.